1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for lifting a bonnet of a blowout preventer.
2. Discussion of the Background
The existing technologies for extracting fossil fuels from offshore or onshore fields use, among other things, a blowout preventer (BOP) for preventing well blowouts. The BOP is conventionally implemented as a valve to prevent the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations. However, various components of the BOP need to be replaced from time to time. An example of a BOP 20 is shown in FIG. 1. The BOP 20 shown in FIG. 1 has, among other things, two ram blocks 22 that are supported by respective piston rods 24 and a corresponding locking mechanism 26. The locking mechanism 26 is configured to lock the rods 24 at desired positions. The two ram blocks 22 are configured to move along a direction parallel to a longitudinal axis of the piston rods 24. The ram blocks 22 may sever a drill line 28 or other tools that cross a vertical wellbore 30 of the BOP 20. However, after cutting the drill line 28 for a number of times, the ram blocks 22 and/or their respective cutting edges need to be inspected and sometimes reworked/replaced. Alternatively, if the ram blocks 22 are designed to seal the well and not to cut a tool, an elastomer provided on a face of the ram blocks 22 needs to be replaced after a certain number of closures of the BOP. For this reason, the BOP 20 of FIG. 1 is provided with a bonnet 32, for each ram block 22, which, for a particular BOP design, can be opened for providing access to the ram blocks. FIG. 2 shows the bonnet 32 having a hinge 34 that rotatably opens the bonnet 32.
Occasionally, the bonnet 32 itself needs to be serviced and then, the bonnet has to be removed from the BOP 20. Also, when the BOP 20 is assembled, the bonnet 32 that may be manufactured at another location needs to be brought next to the BOP 20 and lifted in place. Typically, multiple slings and “come alongs” are placed around the bonnet 32 and are attached to a crane/hoist for handling the bonnet. However, the weight of such a bonnet may reach the order of 3 tons, and thus, when lifting/handling the bonnet (for example, inserting or removing a pin 36 to a hinge 34 for attaching the bonnet to BOP 20) with this type of method, the bonnet can become unstable, making it difficult and unsafe to handle. Also, this procedure may present other risks as the BOP may be situated at a certain height above the floor of the manufacturing facility, or the BOP may be high (few meters) such that a fall of the bonnet from the crane may injure personnel working around or under the BOP.
Further, those skilled in the art would recognize that regular service of the BOP is required for changing the blades and/or elastomer attached to the ram blocks as discussed above. Thus, the BOP bonnets frequently need to be separated from the BOP body to expose and service the ram block. The operation of separating the bonnets from the BOP body is no easy task, and such an operation may require several hours even when utilizing multiple skilled technicians. However, the concern is the amount of down time for the entire rig, which cannot function without the BOP, as millions of dollars of drilling equipment may be idle during the BOP service operation. A solution to this problem is to design BOPS with bonnet-less “doors.” However, these designs have other undesirable features.
Accordingly, it would be desirable to provide a tool that easily attaches to the bonnet of the BOP and facilitates the handling of the bonnet in a safe and efficient way.